It is an option in Europe and the UK on any Focus 2012+. It wasn't an option in the US. US doors didn't even have the accommodations for it. I'm sure that's why it was left off the RS option list in the USA.
Why wasn't it an option in the US? Not sure, but probably because luxury options in general aren't typical on compact cars sold in the US.
I am usually very careful with my door and try to never ding anyone. I remember seeing it on Top Gear and I thought it was the coolest thing ever and I always want it.